In a rotary connector of the type described, for example, in Thoma, J., Einfurung in die Olhydraulik and die hydraulische Systemtechnick, Gierardet Taschenbuch 18 (1973), 2nd Edition, Essen, Federal Republic of Germany. There is the danger that, under certain operational conditions, the relatively moving parts may actually contact one another directly when an equilibrium state is reached between a main pressure in the passage path through the gap, hereinafter referred to as a high pressure space, and an intermediate pressure in an intermediate pressure space communicating with the high pressure space by a leakage orifice slot whose width varies with the gap width between the rings, is reached.
Particularly critical are fast pressure changes, especially pressure drops in the main pressure region.
Stated otherwise, the sliding region is generally provided in an equilibrium state with respect to the counter ring when normal high pressure is maintained in the high pressure space and an intermediate pressure is maintained in the intermediate pressure space. The high pressure space, for example, may be the passages in the rings taken together with the gap between the axially confronting faces of the two rings at which their respective passages open.
Normally this gap communicates with the intermediate pressure space through an outlet or throttle slot or orifice, the width of which varies with the variation in the axial width of the gap. The pressure differential between the high pressure in the high pressure space and the intermediate pressure in the intermediate pressure space determines the axial position of the axially movable ring which, for convenience, will be here equivalent to the sliding ring.
Consequently, with the development of the undesirable conditions mentioned, such as rapid pressure drop in the main pressure steps, the equilibrium can be disrupted and the axially moveable ring can be driven forceably into direct contact with the other ring.
It follows, therefore, that the intermediate pressure responsible for maintenance of substantially constant dimensions of the gaps and thereby ensuring that viscous or fluid direction will be provided between the relatively moving surfaces instead of sliding friction or direct contact, will generally respond to an abrupt drop in the main pressure space with a lag so that at least some period of direct contact cannot be avoided.
Depending upon the response of the coupling with time and the magnitude of the change in the main pressure, a greater or lesser disruption of normal operation can be expected with disturbance in the uniformity of operation and with mechanical wear of significant parts of the system. The mechanical wear is associated with heating and unacceptable friction drag with the overall end result of increased leakage and possibly even breakdown of the coupling.